In Situ Measurement Techniques for Characterizing Pulse Jet Mixing of Slurries

Metrics to characterize mixing are the just suspended velocity (UJS) and the cloud height (HC). Two ultrasonic instruments to characterize pulse jet mixing of slurries were developed and deployed to measure related metrics: the thickness of the settled bed and the concentration within the cloud as a function of elevation [C(Z)]. Ultrasonic Doppler velocimetry was used to measure the thickness of the bed of nonmoving particles (the settled solids layer). During pulse jet mixing at the critical suspension velocity (UCS) the settled solids layer thickness approached zero at the end of the jet pulse. The UCS is related to the just suspended velocity (UJS) for steady mixing. Ultrasonic attenuation was used to measure the suspended solids concentration at locations in the vessel to determine the concentration profile as a function of radial position and elevation. The concentration profile provided data inside the particulate cloud and complemented the visual measurement of the cloud height (HC). The UDV and the ultrasonic concentration probe data are used to evaluate the desired metrics based on relative measurements. The relative measurements are correlated with results obtained from a series of working standards created for each slurry, and used to develop correlations specific to each slurry.